Intramammary lipopolysaccharide infusion induces local and systemic effects on milk components in lactating bovine mammary glands

Localized mammary gland changes in milk composition and venous blood metabolite concentrations result from sterile subclinical mastitis

Subclinical mastitis reduces milk yield and elicits undesirable changes in milk composition, but the mechanisms resulting in reduced milk production in affected mammary glands are incompletely understood. This study investigated the effects of sterile inflammation on mammary gland metabolism by assessing changes in milk and venous blood composition. Mid-lactation primiparous Holstein cows (n = 4) had udder halves randomly allocated to treatments; quarters of 1 udder half were infused with 2 billion cfu of formalin fixed Staphylococcus aureus (FX-STAPH) and quarters of the opposite udder half infused with saline (SAL). Blood samples were collected from the right and left subcutaneous abdominal veins in 2.6 h intervals until 40 h post challenge and analyzed for blood gas and metabolite concentrations. Milk from FX-STAPH udder halves had significantly increased SCS by first milking at 8 h post-challenge. By 16 h post-challenge, FX-STAPH udder halves had increased concentrations of protein and lactate and lower lactose concentrations than SAL udder halves. Milk fat concentrations, milk yields, energy corrected milk yields, and the ferric reducing antioxidant power of milk were not significantly different between SAL and FX-STAPH udder halves. Venous blood of FX-STAPH halves had marginally greater concentrations of saturated O2, partial pressures of O2, and glucose concentrations than SAL halves. Conversely, total and partial pressures of CO2 did not differ between udder half treatments suggesting a shift in local metabolite utilization in FX-STAPH udder halves. These results indicate that changes in milk composition resulting from mastitis are accompanied by changes in some key blood metabolite concentrations. The shift in venous blood metabolite concentrations, along with the marked increase in milk lactate, suggests that local mammary tissue and/or recruited and immune cells alters metabolite usage in mammary tissues. Future studies are needed to quantify the uptake of key milk precursors during mastitis.

Effects of dietary rumen-protected choline supplementation to periparturient dairy cattle on inflammation and metabolism in mammary and liver tissue during an intramammary lipopolysaccharide challenge

The objective of this experiment was to examine the effects of supplementation and dose of rumen-protected choline (RPC) on markers of inflammation and metabolism in liver and mammary tissue during an intramammary lipopolysaccharide (LPS) challenge. Parous Holstein cows were blocked by calving month and randomly assigned within block to receive 45 g/d of RPC (20.4 g/d of choline ions; CHOL45), 30 g/d of RPC (13.6 g/d of choline ions; CHOL30), or no RPC (CON) as a top-dress starting 24 d before expected calving until 21 d postpartum. Cows were alternately assigned within treatment group to either receive an intramammary LPS challenge (200 μg in each rear quarter; Escherichia coli O111:B4) or not at 17 DIM (CHOL45, n = 9; CHOL45-LPS, n = 9; CHOL30, n = 11; CHOL30-LPS, n = 10; CON, n = 10; CON-LPS, n = 9). Hepatic and mammary tissues were collected from all cows on d 17 postpartum. Hepatic and mammary tissues were collected at ∼7.5 and 8 h, respectively, after the LPS challenge. An additional mammary biopsy was conducted on LPS-challenged cows (CHOL45-LPS, CHOL30-LPS, and CON-LPS) at 48 h postchallenge. Hepatic and mammary RNA copy numbers were quantified for genes involved in apoptosis, methylation, inflammation, oxidative stress, and mitochondrial function using NanoString technology. Targeted metabolomics was conducted only on mammary tissue samples (both 8 and 48 h biopsies) to quantify 143 metabolites including choline metabolites, amino acids, biogenic amines and derivatives, organic acids, carnitines, and glucose. Hepatic IFNG was greater in CHOL45 as compared with CON in unchallenged cows, suggesting an improvement in type 1 immune responses. Hepatic CASP3 was greater in CHOL45-LPS as compared with CON-LPS, suggesting greater apoptosis. Mammary IL6 was reduced in CHOL30-LPS cows as compared with CHOL45-LPS and CON-LPS (8 and 48 h). Mammary GPX4 and COX5A were reduced in CHOL30-LPS as compared with CON-LPS (8 h), and SDHA was reduced in CHOL30-LPS as compared with CON-LPS (8 and 48 h). Both CHOL30-LPS and CHOL45-LPS cows had lesser mammary ATP5J than CON-LPS, suggesting that dietary RPC supplementation altered mitochondrial function following LPS challenge. Treatment did not affect mammary concentrations of any metabolite in unchallenged cows, and only 4 metabolites were affected by dietary RPC supplementation in LPS-challenged cows. Mammary concentrations of isobutyric acid and 2 acyl-carnitines (C4:1 and C10:2) were reduced in CHOL45-LPS as compared with CHOL30-LPS and CON-LPS. Taken together, reductions in medium- and short-chain carnitines along with an increase in long-chain carnitines in mammary tissue from CHOL45-LPS cows suggests less fatty acid entry into the β oxidation pathway. Although the intramammary LPS challenge profoundly affected markers for inflammation and metabolism in liver and mammary tissue, dietary RPC supplementation had minimal effects on inflammatory markers and the mammary metabolome.

Intramammary administration of lipopolysaccharides at parturition enhances immunoglobulin concentration in goat colostrum

In newborn ruminants, transfer of passive immunity is essential to obtain protection against pathogens. This study aimed to increase the permeability of the blood-milk barrier using intramammary lipopolysaccharides (LPS) in goats at parturition to modulate colostrum composition. Twenty multiparous Majorera dairy goats were randomly allocated in one of the two experimental groups. The LPS group (n = 10) received an intramammary administration (IA) of saline (2 mL) containing 50 µg of LPS from Escherichia coli (O55:B5) in each half udder at parturition. The control group (n = 10) received an IA of saline (2 mL). Rectal temperature (RT) was recorded, and a blood sample was collected at parturition (before IA). In addition, RT was measured, and blood and colostrum/milk samples were collected on day (d) 0.125 (3 hours), 0.5 (12 hours), 1, 2, 4, 7, 15 and 30 relative to the IA. Goat plasma immunoglobulin G (IgG) and M (IgM) and serum β-hydroxybutyrate, glucose, calcium, free fatty acids, lactate dehydrogenase and total protein concentrations were determined. Colostrum and milk yields as well as chemical composition, somatic cell count (SCC), IgG and IgM concentrations were measured. The MIXED procedure (SAS 9.4) was used, and the model included the IA, time, and the interaction between both fixed effects. Statistical significance was set as P < 0.05. Goats from the LPS group showed higher RT on d 0.125, 0.5 and 4 relative to the IA compared to the control group (PIA×Time = 0.007). Goat serum biochemical variables and plasma IgG and IgM concentrations were not affected by the IA. Colostrum and milk yield as well as chemical composition were not affected by the IA, except for milk lactose percentage that was lower in the LPS group compared to the control group (4.3 ± 0.08 and 4.6 ± 0.08%, respectively PIA = 0.026). Colostrum SCC was higher in the LPS group than in the control group (3.5 ± 0.09 and 3.1 ± 0.09 cells × 106/mL, respectively; PIA = 0.011). Similarly, milk SCC increased in the LPS group compared to the control group (PIA = 0.004). The LPS group showed higher IgG (PIA = 0.044) and IgM (PIA = 0.037) concentrations on colostrum than the control group (31.9 ± 4.8 and 19.0 ± 4.8 mg/mL, 0.8 ± 0.08 and 0.5 ± 0.08 mg/mL, respectively). No differences in milk IgG and IgM concentrations between groups were observed. In conclusion, the IA of LPS at parturition increases RT, SCC and IgG and IgM concentrations in colostrum without affecting either yield or chemical composition.

Systemic and local responses of cytokines and tissue histology following intramammary lipopolysaccharide challenge in dairy cows

During bovine mastitis, immune responses include the release of cytokines and the recruitment of leukocytes, resulting in profound structural and functional changes in the mammary gland. Our aims were to delineate systemic and local cytokine responses and to quantify histological changes in the mammary tissue of lactating cows after acute intramammary lipopolysaccharide (LPS) challenge. Ten multiparous dairy cows were paired to either treatment (TRT) or control (CON) groups. For TRT cows, one side of the udder was randomly assigned to receive treatment with LPS (50 µg in 10 mL of saline, TL) into both the front and rear quarters; the contralateral quarters received saline (10 mL). Udder-halves of CON cows were similarly assigned randomly to receive either saline (10 mL, CS) or no infusion (untreated). Temporal changes in the concentrations of 15 cytokines in the blood (0, 3, 6, 12, and 24 h relative to the LPS infusion) and in mammary tissue (0, 3, and 12 h) were determined, as were concomitant changes in mammary histology. The cytokines IL-6, IL-10, MCP-1, and MIP-1β showed a systemic response as their concentrations were significantly different in the plasma of TRT cows as compared with CON cows after LPS challenge. The cytokines IL-1α, IL-1β, IL-6, IL-8, IL-17A, IL-36RA, IP-10, MCP-1, MIP-1α, MIP-1β, TNF-α, and VEGF-A showed a local response in TL glands, and 8 cytokines, IL-1β, IL-6, IL-10, IL-17A, IL-36RA, IP-10, MIP-1β, and VEGF-A showed systemic changes in the nonchallenged mammary glands adjacent to LPS-infused glands. Endotoxin challenge evoked changes in the histology of mammary tissue that included a 5.2- and 7.2-fold increases in the number of neutrophils in alveolar lumens at 3 h and 12 h, respectively. In summary, LPS challenge induced specific local and systemic responses in cytokine induction and elicited neutrophil infiltration in bovine mammary tissue.

DNA methylation and gene expression changes in mouse mammary tissue during successive lactations: part II - the impact of lactation rank

Mastitis is among the main reasons women cease breastfeeding. In farm animals, mastitis results in significant economic losses and the premature culling of some animals. Nevertheless, the effect of inflammation on the mammary gland is not completely understood. This article discusses the changes to DNA methylation in mouse mammary tissue caused by lipopolysaccharide-induced inflammation after in vivo intramammary challenges and the differences in DNA methylation between 1^st and 2^nd lactations. Lactation rank induces 981 differential methylations of cytosines (DMCs) in mammary tissue. Inflammation in 1^st lactation compared to inflammation in 2^nd lactation results in the identification of 964 DMCs. When comparing inflammation in 1^st vs. 2^nd lactations with previous inflammation history, 2590 DMCs were identified. Moreover, Fluidigm PCR data show changes in the expression of several genes related to mammary function, epigenetic regulation, and the immune response. We show that the epigenetic regulation of two successive physiological lactations is not the same in terms of DNA methylation and that the effect of lactation rank on DNA methylation is stronger than that of the onset of inflammation. The conditions presented here show that few DMCs are shared between comparisons, suggesting a specific epigenetic response depending on lactation rank, the presence of inflammation, and even whether the cells had previously suffered inflammation. In the long term, this information could lead to a better understanding of the epigenetic regulation of lactation in both physiological and pathological conditions.Abbreviations: RRBS, reduced representation bisulphite sequencing; RT-qPCR, real-time quantitative polymerase chain reaction; MEC, mammary epithelial cells; MaSC, mammary stem cell; TSS, transcription start site; TTS, transcription termination site; UTR, untranslated region; SINE, short interspersed nuclear element; LINE, long interspersed nuclear element; CGI, CpG island; DEG, differentially expressed gene; DMC, differentially methylated cytosine; DMR, differentially methylated region; GO term, gene ontology term; MF, molecular function; BP, biological process.

Effects of heat stress abatement on systemic and mammary inflammation in lactating dairy cows

To examine the effects of evaporative cooling on systemic and mammary inflammation of lactating dairy cows, 30 multiparous Holstein cows (parity = 2.4, 156 d in milk) were randomly assigned to 1 of 2 treatments: cooling (CL) with fans and misters or not (NC). The experiment was divided into a 10-d baseline when all cows were cooled, followed by a 36-d environmental challenge when cooling was terminated for NC cows. The onset of environmental challenge was considered as d 1. Temperature-humidity index averaged 78.4 during the environmental challenge. Milk yield and dry matter intake (DMI) were recorded daily. Blood and milk samples were collected from a subset of cows (n = 9/treatment) on d -3, 1, 3, 7, 14, and 28 of the experiment to measure cortisol, interleukin 10 (IL10), tumor necrosis factor-α (TNF-α), haptoglobin, and lipopolysaccharide binding protein (LBP). Mammary biopsies were collected from a second subset of cows (n = 6/treatment) on d -9, 2, 10, and 36 to analyze gene expression of cytokines and haptoglobin. A subset of cows (n = 7/treatment) who were not subjected to mammary biopsy collection received a bolus of lipopolysaccharides (LPS) in the left rear quarter on d 30 of the experiment. Blood was sampled from cows and milk samples from the LPS-infused quarter were collected at -4, 0, 3, 6, 12, 24, 48, and 96 h relative to infusion, for analyses of inflammatory products. Deprivation of cooling decreased milk yield and DMI. Compared with CL cows, plasma cortisol concentration of NC cows was higher on d 1 but lower on d 28 of the experiment (cooling × time). Deprivation of cooling did not affect circulating TNF-α, IL10, haptoglobin, or LBP. Compared with CL cows, NC cows tended to have higher milk IL10 concentrations but did not show effects in TNF-α, haptoglobin, or LBP. No differences were observed in mammary tissue gene expression of TNF-α, IL10, and haptoglobin. Milk yield declined after LPS infusion but was not affected by treatment. Compared with CL cows, NC cows had greater milk somatic cell count following intramammary LPS infusion. Non-cooled cows had lower circulating TNF-α and IL10 concentrations and tended to have lower circulating haptoglobin concentrations than CL cows. Milk IL10 and TNF-⍺ concentrations were higher 3 h after LPS infusion for NC cows compared with CL cows. Additionally, NC cows tended to have higher milk haptoglobin concentration after LPS infusion than CL cows. In conclusion, deprivation of evaporative cooling had minimal effects on lactating cows' basal inflammatory status, but upregulated mammary inflammatory responses after intramammary LPS infusion.

Effects of oyster glycogen intramammary challenge on primiparous cow milk somatic cell counts, milk yields, and milk composition

Mastitis is a common and costly disease in the dairy industry that reduces milk production in affected mammary glands. The local mechanisms that result in reduced milk production of affected mammary glands are incompletely understood; elucidation of these mechanisms is dependent on the use of hypothesis testing studies, but few experimental models exist. The objective of this study was to develop a mastitis challenge model, using a split udder design, to reduce milk yields by approximately 15% in udder halves challenged with oyster glycogen, a known inducer of leukocyte recruitment, relative to udder halves treated with saline. Four primiparous Holstein cows in mid lactation were used. One udder half of each cow was randomly selected and challenged with oyster glycogen (OYGLN), and the opposite udder half was treated with saline (SAL). Milk yields and components were measured at each milking (3×/d) for 3 d postchallenge. No signs of clinical mastitis were observed. Milk somatic cell scores, yields, and components were similar between OYGLN and SAL udder halves at time of challenge. Milk somatic cell scores markedly increased in OYGLN halves postchallenge and were greater than SAL halves for the duration of the trial. Lactose concentrations of OYGLN udder halves were transiently lower than in SAL udder halves, but protein concentrations were greater at 2 milkings postchallenge in OYGLN halves. Milk yields and energy-corrected milk yields did not differ between OYGLN and SAL udder halves overall, nor at any postchallenge milking. A single intramammary challenge of oyster glycogen was unsuccessful in eliciting a disparity in milk yields between challenged and saline control udder halves despite the marked leukocyte infiltration observed in the former. These results indicate an incomplete understanding of how milk yields are reduced in mammary glands affected by subclinical mastitis and that transient somatic cell recruitment and infiltration alone do not directly reduce milk yields during subclinical mastitis.

Graduate Student Literature Review: Systemic mediators of inflammation during mastitis and the search for mechanisms underlying impaired lactation

The negative effect of mastitis on lactation is well established, yet the mechanisms causing reduced milk production in the afflicted dairy cow are not. As one of the major inflammatory diseases in the dairy industry, mastitis has rightly received considerable research interest for decades. However, the focus on distinct, pathologic effects in mastitic glands has largely overlooked systemic effects on noninflamed mammary glands. This is particularly evident in the severe, acute response to the potent inflammatory mediator, lipopolysaccharide (LPS). Whereas secretory cell death, impaired tight junctions, and migration of leukocytes are locally restricted to an inflamed, LPS-challenged gland, changes in milk yield and milk components may be detectable in all mammary glands. Further, these differences extend to the mammary transcriptome. Notably, few transcriptomic studies have been designed to test for effects of systemic mediators of inflammation on gene expression. Relevant changes in the noninflamed mammary gland, identified through biochemical analyses and transcriptional studies, warrant further research. Current evidence suggests proinflammatory cytokines play a role in regulating lactose synthesis, but additional candidates and mechanisms continue to be identified. Ultimately, understanding how systemic mediators of inflammation affect mammary function may lead to the development of interventions that enable more efficient milk production without sacrificing the benefits of inflammation.

Menthol Targeting AMPK Alleviates the Inflammatory Response of Bovine Mammary Epithelial Cells and Restores the Synthesis of Milk Fat and Milk Protein

Mastitis is one of the most serious diseases that causes losses in the dairy industry, seriously impairing milk production and milk quality, and even affecting human health. Menthol is a cyclic monoterpene compound obtained from the stem and leaves of peppermint, which has a variety of biological activities, including anti-inflammatory and antioxidant activity. The purpose of this study was to investigate the preventive effect of menthol on the lipopolysaccharide-induced inflammatory response in primary bovine mammary gland epithelial cells (BMECs) and its anti-inflammatory mechanism. First, BMECs were isolated and amplified from the udders of Holstein cows by enzymatic hydrolysis. BMECs were treated with menthol (10, 50, 100, 200 μM) for 1h, followed by lipopolysaccharide (5μg/ml) for 12 h. Lipopolysaccharide treatment upregulated the protein levels of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (INOS) and the mRNA abundance of tumor necrosis factor α (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β), while menthol was able to inhibit this effect. The inhibitory effect of menthol on proinflammatory factors was significantly reduced when autophagy was blocked using 3-Methyladenine (5μg/ml), an inhibitor of autophagy. Furthermore, lipopolysaccharide treatment reduced the expression levels of milk lipids and milk proteins, which were inhibited by menthol. In addition, menthol (200 μM) treatment was able to significantly upregulate the expression level of autophagy-related protein LC3B, downregulate the expression level of P62, promote the expression abundance of autophagy-related gene mRNA, and enhance significantly enhance autophagic flux. Interestingly, treatment of BMECs with menthol (200 μM) promoted the phosphorylation of AMP-activated protein kinase (AMPK) and unc-51 like kinase 1 (ULK1) and increased the nuclear localization of nuclear factor-E2 associated factor 2 (Nrf-2). When the AMPK pathway was blocked using compound C (10μg/ml), an inhibitor of AMPK, autophagy was significantly inhibited. Autophagy levels were significantly decreased after blocking the Nrf-2 pathway using ML385 (5μg/ml), an inhibitor of Nrf-2. Overall, the data suggest that menthol activates the AMPK-ULK1 pathway to initiate the onset of autophagy and maintains the level of autophagy through the AMPK-Nrf-2 pathway. In conclusion, the findings suggest that menthol may alleviate the inflammatory response in BMECs via the AMPK/ULK1/Nrf-2/autophagy pathway.

Localized and Systemic Inflammatory Mediators in a Murine Acute Mastitis Model

Introduction

Milk depression is the major driver of economic loss due to mastitis in dairy animals. The aim of this study was to identify potential mediators of milk depression by investigating the local and systemic changes in gene expression or cytokine production during endotoxin challenge of the mammary gland in a mouse model.

Methods

The left and right sides of the 4th pair of mouse mammary glands were alternatively injected with either lipopolysaccharide (LPS, Escherichia coli 055: B5, 50 μL of 0.4 mg/mL) or sterile PBS through the teat meatus 3 days postpartum (n = 9). The 4th glands were individually collected 12 h after LPS injection and analyzed to identify gene expression changes by RNA sequencing and real-time PCR, and the plasma was collected before and after LPS challenge and analyzed to determine the levels of 32 cytokines.

Results

Transcriptome analysis showed that in addition to strong pro-inflammatory responses, which included granulocyte and monocyte migration and cytokine production and signaling, the LPS-treated glands exhibited strong ubiquitin-mediated and immune-mediated proteasome activation and an increase in nitric oxide-mediated oxidative stress. Furthermore, LPS induced a down-regulation in vesicle membrane, vesicle-mediated trafficking, and metabolic processes of amino acids and other organic molecules in the mammary gland. Of the 32 cytokines analyzed, the levels of 24 (mainly IL-6, G-CSF, MCP-1, RANTES, MIG, MIP-1b, KC, MIP-2, IP-10, and TNFα) were increased or tended to increase in the blood after LPS treatment, and only the levels of IL-9 were decreased. In the mammary gland after LPS challenge, the levels of IL-5, IL-6, IP-10, LIF, MCP-1, MIP-2, and TNFα were significantly increased, and the levels of INFΥ, IL-2, IL-4, IL-10, and IL-12 (p40) were decreased.

Discussion

These observations provide potential markers and targets for further studies on the prevention and treatment of gram-negative bacteria-induced mastitis.

Hypogalactia in mammary quarters adjacent to lipopolysaccharide-infused quarters is associated with transcriptional changes in immune genes

Infusion of lipopolysaccharides (LPS) into a mammary gland can provoke inflammatory responses and impair lactation in both the infused gland and neighboring glands. To gain insight into the mechanisms controlling the spatiotemporal response to localized mastitis in lactating dairy cows, we performed RNA sequencing on mammary tissue from quarters infused with LPS, neighboring quarters in the same animals, and control quarters from untreated animals at 3 and 12 h postinfusion. Differences in gene expression were annotated to Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Comparing mammary transcriptomes from all 3 treatments revealed 3,088 and 1,644 differentially expressed (DE) genes at 3 and 12 h, respectively. Of these genes, >95% were DE only in LPS-infused quarters and represented classical responses to LPS: inflammation, apoptosis, tissue remodeling, and altered cell signaling and metabolism. Although relatively few genes were DE in neighboring quarters (56 at 3 h; 74 at 12 h), these represented several common pathways. At 3 h, tumor necrosis factor (TNF), nuclear factor-κB, and nucleotide-binding and oligomerization domain (NOD)-like receptor signaling pathways were identified by the upregulation of anti-inflammatory (NFKBIA, TNFAIP3) and cell adhesion molecule (VCAM1, ICAM1) genes in neighboring glands. Additionally, at 12 h, several genes linked to 1-carbon and serine metabolism were upregulated. Some responses were also regulated over time. The proinflammatory response in LPS-infused glands diminished between 3 and 12 h, indicating tight control over transcription to re-establish homeostasis. In contrast, 2 glucocorticoid-responsive genes, FKBP5 and ZBTB16, were among the top DE genes upregulated in neighboring quarters at both time points, indicating potential regulation by glucocorticoids. We conclude that a transient, systemic immune response was sufficient to disrupt lactation in neighboring glands. This response may be mediated directly by proinflammatory factors from the LPS-infused gland or indirectly by secondary factors released in response to systemic inflammatory signals.